Lead frame and semiconductor device

ABSTRACT

A lead frame includes a die pad for mounting thereon a semiconductor chip having a plurality of electrodes, a plurality of leads for electrical connection with the plurality of electrodes of the semiconductor chip, an outer frame disposed on the periphery of the die pad for supporting the die pad and the plurality of leads, and a resin guide portion extending to the vicinity of the die pad from the outer frame for guiding molten resin over and under the semiconductor chip during resin packaging. A semiconductor device manufacturing method includes mounting a semiconductor chip having electrodes on a substrate having a resin guiding portion for guiding a resin over and under the semiconductor chip during resin packaging; electrically connecting leads on the substrate to the electrodes; positioning the semiconductor chip and the substrate between a pair of mold halves injecting a molten resin into the mold to fill the cavity; and solidifying the resin.

This application is a continuation of application Ser. No. 07/330,212,filed Mar. 29, 1989 now abandoned.

BACKGROUND OF THE INVENTION

1. Field of the Invention:

The present invention relates to a lead frame by which a highly reliablesemiconductor device is provided. The present invention also relates toa semiconductor device in which a semiconductor chip is packaged with aresin, as well as a manufacturing method therefor.

2. Description of the Related Art:

FIG. 1 is a plan view illustrating the relationship between a die and alead frame with a semiconductor chip mounted thereon when thesemiconductor chip is packaged with a resin. In FIG. 1, a rectangularsemiconductor chip 1 is mounted on a die pad 3 located substantially atthe central portion of a lead frame 8. The die pad 3 is connected to andsupported through supporting leads 7 extending to outer frames 2 of thelead frame 8 which are disposed parallel to each other. A plurality ofleads 4 are disposed in opposed relation with the semiconductor chip 1on each of the long sides of the semiconductor chip 1. Each of the leads4 includes an inner lead 4a disposed in opposed relation with thesemiconductor chip 1, and an outer lead 4b extending from the end of theinner lead 4a remote from the semiconductor chip 1. The leads 4 on eachof the long sides of the semiconductor chip 1 are connected with eachother by a tie bar 5 at the substantially central portions thereof.Unillustrated electrode pads formed on the surface of the semiconductorchip 1 are electrically connected to the corresponding inner leads 4a bywires 6 made of, for example, gold.

Such a lead frame-semiconductor chip assembly is packaged with a resinusing a mold 10. As shown in FIG. 2, the mold 10 includes an upper moldhalf 10a and a lower mold half 10b. The upper and lower mold halves 10aand 10b respectively have rectangular cavity halves 11a and 11b andgroove-shaped gate halves 12a and 12b which communicate with the cavityhalves 11a and 11b. The portions of the gate halves 12a and 12b, whichserve as the entrance to the cavity halves 11a and 11b, form gate ports13a and 13b having a rectangular cross-section.

Resin packaging will be conducted as follows. First, the semiconductorchip 1 is mounted on the die pad 3 of the lead frame 8, and thisleadframe-chip assembly is carried between the upper and lower moldhalves 10a and 10b and is located at a predetermined position, as shownin FIG. 1. Thereafter, the upper and lower mold halves 10a and 10b arerespectively lowered and raised to sandwich the lead frame 8therebetween, as shown in FIG. 2. At this time, the upper and lower moldhalves 10a and 10b make contact with the outer frames 2 of the leadframe 8, the leads 4 and part of the hanging leads 7. Further, thecavity halves 11a and 11b in combination form a cavity 11 within themold 10 with the semiconductor chip 1 on the die pad 3 beingaccommodated therein. Furthermore, the pair of gate halves 12a and 12bform a tubular gate 12, which communicates with the cavity 11 through agate port 13 formed by the pair of gate port halves 13a and 13b.

Next, a molten thermosetting resin 14 is injected into the cavity 11through the gate 12 formed in the mold 10 under a predeterminedpressure. The resin 14 is divided into two flows by the outer frame 2 ofthe lead frame 8 which is disposed in such a manner that it separatespart of the interior of the gate 12 into upper and lower portions. Theseportions guide these flows toward the gate port 13 along the upper andlower sides of the outer frame 2. Although a large part of the areawithin the cavity 11 is separated into upper and lower portions by thedie pad 3 having the semiconductor chip 1 mounted thereon, no outerframe 2 exists in the vicinity of the gate port 13, so the resin flows14 that have passed along the upper and lower sides of the outer frame 2meet each other near the gate port 13. Thereafter, the resin 14 entersand fills the cavity 11, as shown by the arrows in FIG. 3.

In this state, the thermosetting resin 14 within the cavity 11 is heatedto a predetermined temperature to set it. Subsequently, the upper andlower mold halves 10a and 10b are respectively raised and lowered toopen the mold 10, and the leadframe-chip assembly is removed from themold 10. Next, the leadframe-chip assembly is subjected to a subsequentprocess in which the tie bars 5 are cut and the leads 4 are bent,thereby completing a semiconductor device.

As stated above, although the resin 14 injected toward the cavity 11 isdivided into two upper and lower flows by the outer frame 2 within thegate 12, these two flows meet each other in the vicinity of the gateport 13. Thereafter, the resin 14 is again divided into upper and lowerflows to be introduced over and under the semiconductor chip 1,respectively. At this time, these new flows are, however, not alwaysuniformly introduced over and under the chip 1. The flows generally havedifferent resistances due to the wires 6 the positions of thesemiconductor chip 1 and the die pad 3 in the cavity 11 and so on. Inconsequence, if the lead frame 8 is not supported so firmly by the leads7, or if the viscosity of the resin 14 is large, the die pad 3 may bedeformed or the semiconductor chip 1 misplaced because of the unbalancedflow pressure of the resin 14, as shown in FIG. 3. This may cause breaksof the wires 6 that connect the electrodes of the semiconductor chip 1to the inner leads 4a in the resin-packaged semiconductor device.Alternatively, this may make the upper and lower portions of thepackaging resin 14 with respect to the semiconductor chip 1 unequal intheir thickness, thus leading to the deterioration in the moistureresistance of the semiconductor device.

SUMMARY OF THE INVENTION

The present invention is directed to obviating the aforementionedproblems by providing a lead frame by which a semiconductor devicehaving high reliability can be produced. Another object of the presentinvention is to provide a highly reliable semiconductor device and amanufacturing method thereof.

According to one aspect of the present invention, a lead frame comprisesa die pad for mounting thereon a semiconductor chip, the semiconductorchip being provided with a plurality of electrodes, a plurality of leadsdisposed in opposed relation with the die pad for electrical connectionwith the plurality of electrodes of the semiconductor chip, outer framemeans disposed on the periphery of the die pad for supporting the diepad and the plurality of leads, and resin guide means extending to thevicinity of the die pad from the outer frame means for guiding a moltenresin over and under the semiconductor chip during resin packaging.

According to another aspect of the present invention, a semiconductordevice comprises a semiconductor chip having electrodes, leadselectrically connected to the electrodes of the semiconductor chip, apackage body which is formed of a resin injected into a mold for moldingthe semiconductor chip and part of the leads, and a resin guidingportion buried in the package body for guiding the resin over and underthe semiconductor chip in the mold during resin packaging.

According to still another aspect of the present invention, asemiconductor device manufacturing method comprises the steps ofmounting a semiconductor chip having electrodes on a substrate means,the substrate means being provided with leads and a resin guidingportion for guiding a resin over and under the semiconductor chip duringresin packaging;

electrically connecting the leads on the substrate means to theelectrodes of the semiconductor chip;

positioning the semiconductor chip mounted on the substrate meansbetween a pair of mold halves with the semiconductor chip disposed at acorresponding position to cavity halves of the mold halves, the resinguiding portion of the substrate means being aligned with gate halves ofthe mold halves;

closing the mold halves to sandwich the substrate means between partingsurfaces of the mold halves, the resin guiding portion being sandwichedbetween the gate halves of the mold halves to separate the gate intoupper and lower portions, the end of the resin guiding portionprotruding into a cavity formed by the cavity halves of the mold halves;

injecting a molten resin into the cavity through the gate, the moltenresin passing through the upper and lower portions of the gate and beingintroduced into the cavity to fill the cavity; and

solidifying the resin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view illustrating the relationship between a mold and alead frame when a conventional semiconductor device is packaged with aresin;

FIGS. 2 and 3 are sections taken along the line II--II of FIG. 1respectively illustrating resin packaging processes;

FIG. 4 is a plan view illustrating the relationship between a mold and alead frame when a semiconductor device of a first embodiment accordingto the present invention is plastically packaged with a resin;

FIG. 5 and 6 are sections taken along the line V--V of FIG. 4respectively illustrating resin packaging processes;

FIG. 7 is a plan view illustrating the relationship between a mold and alead frame produced when a semiconductor device of a second embodimentaccording to the present invention is packaged with a resin;

FIG. 8 is a plan view illustrating the relationship between a mold and alead frame produced when a semiconductor device of a third embodimentaccording to the present invention is packaged with a resin; and

FIG. 9 is section taken along the line IX--IX of FIG. 8 illustrating theresin packaging process.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Embodiments of the present invention will be described below withreference to the accompanying drawings.

A first embodiment of the present invention will first be described withreference to FIGS. 4 to 6. In FIG. 4, a rectangular semiconductor chip 1is mounted on a die pad 3 located substantially at the central portionof a lead frame 8. The die pad 3 is connected to and supported throughsupporting leads 7 to outer frames 2 of the lead frame 8 which aredisposed parallel to each other. A plurality of leads 4 are disposed oneach of the long sides of the semiconductor chip 1. Each of the leads 4includes an inner lead 4a disposed in opposed relation with thesemiconductor chip 1, and an outer lead 4b extending from the end of theinner lead 4a remote from the semiconductor chip 1. The leads 4 on eachof the long sides of the semiconductor chip 1 are connected with eachother by a tie bar 5 at the substantially central portions thereof.Unillustrated electrode pads formed on the surface of the semiconductorchip 1 are electrically connected to the corresponding inner leads 4a bywires 6 made of, for example, gold. Part of one of the outer frames 2 ofthe lead frame 8 protrudes toward the die pad 3 near the adjacent sideedge thereof to form a resin guiding portion 15.

Such a lead frame semiconductor chip assembly is packaged with a resinusing a mold 10. The mold 10, like the conventional mold shown in FIGS.1 to 3, comprises an upper mold half 10a and a lower mold half 10b. Theupper and lower mold halves 10a and 10b respectively have rectangularcavity halves 11a and 11b and groove-shaped gate halves 12a and 12bwhich respectively communicate with the cavity halves 11a and 11b. Theportions of the gate halves 12 and 12b which serve as the entrance tothe cavity halves 11a and 11b form gate port halves 13a and 13b having arectangular cross-section. The resin guiding portion 15 is formed tocover the gate port halves 13a, 13b and part of the gate halves 12a, 12bwhen the leadframe-semiconductor chip assembly is disposed in the mold10.

Resin packaging will be conducted as follows: First, the semiconductorchip 1 is mounted on the die pad 3 of the lead frame 8, and this leadframe-chip assembly is placed between the upper and lower mold halves10a and 10b of the opened mold 10 and is located at a predeterminedposition, as shown in FIG. 4. At this time, the resin guiding portion 15of the lead frame 8 is located on the gate half 12b and the gate porthalf 13b of the lower mold half 10b to cover them, with the distal innerend thereof extending into and above the cavity half 11b of the lowermold half 10b.

Thereafter, the upper and lower mold halves 10a and 10b are respectivelylowered and raised to sandwich the lead frame 8 therebetween, as shownin FIG. 5. At this time, the upper and lower mold halves 10a and 10bmake contact with the outer frames 2 of the lead frame 8, the leads 4and part of the hanging leads 7. Further, the cavity halves 11a and 11bin combination form a cavity 11 within the mold 10 with thesemiconductor chip 1 on the die pad 3 being accommodated therein.Furthermore, the pair of gate halves 12a and 12b form a tubular gate 12,which communicates with the cavity 11 through a gate port 13 formed bythe pair of gate port halves 13a and 13b. Further, while the distal orinner end of the resin guiding portion 15 of the lead frame 8 is locatedin the cavity 11, the basal or outer end portion of the resin guidingportion 15 and the outer frame 2 connected therewith extend through partof the gate 12 and the guide port 13, thereby dividing the space in thevicinity of the gate port 13 into upper and lower portions which aresubstantially completely separated from each other.

Next, a molten thermosetting resin 14 is injected into the cavity 11through the gate 12 formed in the mold 10 under a predeterminedpressure. The injected resin 14 is separated and divided into upper andlower flows at a location halfway between the gate 12 by the outer frame2 and the resin guiding portion 15 of the lead frame 8, and these twoflows then proceed toward the gate port 13. The resin flows which haveentered the cavity 11 through the gate port 13 are kept separated by theresin guiding portion 15. One flow of the resin 14 which has passedthrough the gate half 12a and the gate port half 13a of the upper moldhalf 10a is introduced into the upper portion of the cavity 11 locatedabove the semiconductor chip 1, while the other flow of the resin 14which has passed through the gate half 12b and the gate port half 13b ofthe lower mold half 10b is introduced into the lower portion of thecavity 11 located below the semiconductor chip 1, as shown by the arrowsin FIG. 6. The resin guiding portion 15 thus controls the flows of theresin 14 into the cavity 11 so that the resin 14 is substantiallyuniformly injected into the upper and lower portions of the cavity 11located over and under the semiconductor chip 1.

Once the cavity 11 has been completely filled with the resin 14, thethermosetting resin 14 within the cavity 11 is heated to a predeterminedtemperature so that it is caused to set. Subsequently, the upper andlower mold halves 10a and 10b are respectively raised and lowered toopen the mold 10, and the lead frame-chip assembly is removed from themold 10. Next, the lead frame-chip assembly is subjected to a subsequentprocess in which the tie bars 5, the supporting leads 7 and the resinguiding portion 15 are cut and the leads 4 are then bent, therebycompleting a semiconductor device.

As stated above, since such a semiconductor device is formed byuniformly injecting the resin 14 over and under the semiconductor chip1, misplacement of the semiconductor chip 1 and deformation of the leadframe 8 do not occur during packaging. This reduces the risk that theportions of the packaging resin 14 respectively located over and underthe semiconductor chip 1 will have unequal thicknesses or that the wires6 will break, thereby providing a highly reliable semiconductor device.

In this embodiment, although the resin guiding portion 15 of the leadframe 8 which separates part of the gate 12 and the gate port 13 of themold 10 into upper and lower portions has a width larger than that ofthe gate 12 as viewed from above, it may have other shapes besides therectangular form shown in FIG. 4.

Further, as shown in FIG. 7, the portion of the outer frame 2 of thelead frame 8 which is located above the gate half 12b of the lower moldhalf 10b may be widened toward the die pad 3 so that it extends abovethe cavity half 11b of the lower mold half 10b to form a wide orenlarged resin guiding portion 15a. In this case, since a larger part ofthe cavity 11 of the mold 10 is separated into upper and lower portionsby the wide or enlarged resin guiding portion 15a, more accurate controlof the resin flow 14 can be ensured during the resin packaging.

FIG. 8 is a plan view showing a semiconductor device of a thirdembodiment of the present invention. In this semiconductor device,electrodes of a semiconductor chip 1 are formed as bump electrodes,which are electrically connected directly to inner leads 4a of leads 4formed on a flexible insulating film 17 made of, for example, apolyimide. The central portion of the film 17 includes a rectangularopening 18 in which the semiconductor chip 1 is accommodated. The film17 also has a plurality of outer lead holes 19 around the opening 18.The leads 4 are supported by supporting portions 20 which are providedbetween the opening 18 and the outer lead holes 19. The supportingportions 20 are secured to the film 17 through bridging portions 21 eachof which is located between the mutually adjacent ones of the outer leadholes 19.

The gate half 12b of the lower mold half 10b is formed such that it islocated below one of the bridging portions 21 of the film 17 when thefilm 17 is mounted thereon. The bridging portion 21 located above thegate half 12b and the supporting portion 20 that continues from thisbridging portion 21 in combination form a resin guiding portion 15b ofthis embodiment.

When the film-chip assembly is to be packaged, the assembly is placedbetween the upper and lower mold halves 10a and 10b of the mold 10, asshown in FIG. 9, and the resin 14 is injected into the cavity 11 throughthe gate 12 formed by the gate halves 12a and 12b of the upper and lowermold halves 10a and 10b.

At this time, the resin 14 is separated into upper and lower flowswithin the gate 12 of the mold 10 by the resin guiding portion 15b, andthese flows are respectively introduced into the cavity 11 through thegate 12 of the mold 10. In consequence, the resin 14 is injected overand under the semiconductor chip 1 uniformly, making it possible tofabricate a highly reliable semiconductor device.

Any of the above-described embodiments employs the mold 10 in which thegate port halves 13a and 13b of the upper and lower mold halves 10a and10b form the gate port 13 having a rectangular cross-section and inwhich this gate port 13 is separated into upper and lower portions bythe resin guiding portion 15. However, the gate port 13 may have anysuitable cross-section, shape or size, so long as it allows the resin 14to be uniformly introduced into the upper and lower portions of thecavity 11.

What is claimed is:
 1. A lead frame comprising:a die pad having opposedfirst and second sides defining a thickness direction perpendicularthereto, said first side for mounting thereon a semiconductor chipincluding a plurality of electrodes; a plurality of leads disposedperipherally around said die pad for electrical connection withrespective electrodes of the semiconductor chip; and an outer framemember peripherally disposed around said die pad from which saidplurality of leads extend including supporting leads extending to andsupporting said die pad and resin guide means extending toward said diepad from said outer frame member for disposition (i) within a moldingcavity of a mold that receives said die pad, (ii) centrally disposed,relative to the thickness direction, within a resin gate groove of themold through which molten resin is supplied to the molding cavity, saidgate groove having a height generally parallel to the thicknessdirection and a width transverse to the thickness direction, and (iii)extending fully across the width of the gate groove for dividing themolten resin into two separated streams in the gate groove and forguiding the two streams of molten resin flowing through the gate groovealong the resin guiding means respectively to said first and secondsides of said die pad and to the semiconductor chip during resinencapsulation of said lead frame and the semiconductor chip withoutintermixing of the two streams in the gate groove and adjacent the gategroove in the molding cavity.
 2. A resin packaged semiconductor devicecomprising:a die pad having opposed first and second sides defining athickness direction perpendicular thereto; a semiconductor chipincluding a plurality of electrodes, said chip being mounted on thefirst side of said die pad; a plurality of leads electrically connectedto respective electrodes of said semiconductor chip; and a molden resinencapsulating said semiconductor chip, part of said leads, and a portionof resin guiding means that was disposed within a molding cavity of amold that received said die pad during resin encapsulation, that wascentrally disposed, relative to the thickness direction, within a resingate groove of the mold through which molten resin has been supplied tothe molding cavity for forming the molded resin, said gate groove havinga height generally parallel to the thickness direction and a widthtransverse to the thickness direction and extending fully across thewidth of the gate groove for dividing the molten resin into twoseparated streams in the gate groove and for guiding the two streams ofmolten resin flowing through the gate groove along the resin guidingmeans respectively to said first and second sides of said die pad and tothe semiconductor chip during formation of said molded resin withoutintermixing of the two streams in the gate groove and adjacent the gategroove in the molding cavity.